The invention is based on a waveguide multiplexer/demultiplexer. A waveguide multiplexer/demultiplexer is known comprising a rectangular collecting waveguide short-circuited at one end and coupled to a plurality of tunable waveguide filters at least on one of its sidewalls, the waveguide filters being tunable to different frequency bands.
Such a waveguide multiplexer/demultiplexer has been disclosed in PCT Application WO 88/03711. Here, two waveguide filters are in each case coupled in the same cross-sectional plane to the collecting waveguide, to be precise in each case one waveguide filter to one of two mutually opposite side walls. The coupling is effected via pins which project on one end into the collecting waveguide and on the other end into the waveguide filter, through its side walls. The same document also discloses a waveguide multiplexer/demultiplexer in the case of which waveguide filters are coupled at the ends via slots in two mutually opposite side walls of a collecting waveguide. The waveguide filters are alternately coupled along the collecting waveguide to the opposite side walls, so that there is always a coupling opening for a waveguide filter in a cross-sectional plane of the collecting waveguide.
This known type of coupling of waveguide filters to a collecting waveguide results in an extremely long physical length of the multiplexer/demultiplexer, particularly if it is intended to be designed for a very large number (for example 12) of frequency channels. Since such waveguide multiplexers/demultiplexers are used in the field of space flight, it is disadvantageous if their physical shapes are very voluminous.